Post PM-833T Spindle Bore Runout

If you actually bored out your spindle, that would also make any collet chuck you might have used inaccurate. A new spindle might be your best option. The amount of run-out you are citing is going to have a significant impact on end mill life, accuracy and finishes.
 
When I got the machine the Interstate collet would not insert. The threaded end measured maybe 2.5 ten thousandth inch under .949. From what I could find .949 to .9495 is the standard size for the threaded end of an R8 collet. I felt the spindle was slightly undersized.

I only enlarged the upper end. I didn't machine the taper. So any deflection would occur with a lateral load. I don't think that will have any ill affects on the end mills.
 
I would be interested in the OD of the threaded end of a high precision collet.

I also can not find the specs for the ID of the upper end of the spindle cavity. It would be interesting to know how close the collet and spindle measurements are to one another.
 
All of my R8 collets measure between 0.94920-0.94945", the R8 collet specification is 0.94960" but probably varies by manufacturer. I would assume the spindle diameter would be 0.9500", spindle tolerance is usually within 0.0002" but once again is manufacturer dependent. The wiggle test doesn't really tell you much, it is all what the cutter does under load. In this setting the longevity of end mills will not be an issue, under CNC conditions it would be different. I think the bottom line is if something is not fitting in a new machine, I would work out/evaluate all other options including replace the spindle, before modifying spindle to collet mating surfaces. If there was a defect then it should have been addressed by the manufacture. You also did not indicate if you remove the guide pin and if other R8 tooling did not fit. This was the differential for me when I had a problem with my initial R8 collets, other R8 tooling like drill chucks fit w/o any problems. Just my 2 cents on the issue.
 
The guide pin was out when the collet got stuck. The two arbors that came with the machine were a snug fit. The drill chuck was a smooth fit.

Based on your measurements your collets wouldn't have fit since mine is slightly smaller.

The manufacturer said I could return the spindle and they would check it out. Perhaps it was unwise but I didn't want to take the machine apart. I solved my problem by enlarging the upper end of the spindle.

I have milled the edges of a 1/2" flat bar with a 1/2" end mill. The operation was accurate and the adjacent faces square when compared to my Starrett ruler (I don't have a machinist square). I took .0625 inches off of the 1/2" edge with each pass.

The measurement of the upper and lower sides was within about a quarter thousandth inch top compared to bottom.

I don't know how much pressure would be required to deflect the collet. The oversized upper end of the socket will not likely be a problem for the work I do.

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mksj, do your collets slip in easily or are they a snug fit? I would think if your spindle is only two ten thousandth inch larger than your collet it would take some finagling to get them in.
 
Bill Kirkley said:
I would be interested in the OD of the threaded end of a high precision collet.
Click to expand...

I use Crawford R8 collets. All measure between 0.9491-0.9493. I have one Yuasa collet at 0.9493". Hardinge collets are the standard in my opinion but Crawford and Yuasa are quite good as well.

Its your call as to how accurate or inaccurate the spindle needs to be for what you're doing. For myself, I would bite the bullet and order a new spindle from PM and rectify the situation. Then I would buy a really good ER chuck and some good collets and be done with it.
 
I agree with Mike - get a new spindle that is on-spec. Sometime down the road you will be glad you did.
 
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